What Does the Triangular Cord Sign Mean on Ultrasound?

Hearing medical terms on your baby’s ultrasound report can be frightening, especially when you are worried about their liver. If a radiologist mentions the triangular cord sign, it is important to know this is an imaging clue, not a tumor. The triangular cord sign refers to a bright, triangular or tubular band of scar-like (fibrous) tissue seen at the porta hepatis—the central area where major blood vessels, like the portal vein, enter the liver ^[1][2]. In babies with suspected biliary atresia, this bright spot represents the damaged, scarred remains of the bile ducts just outside the liver ^[1]. Seeing this sign on a non-invasive ultrasound is an important finding that helps doctors evaluate whether a child might have biliary atresia ^[3].

What Do the Ultrasound Results Mean?

Radiologists evaluate the triangular cord sign based on how accurately it can identify the disease (its sensitivity and specificity). We can break down what these statistics mean for your baby’s scan:

• When the sign is present (High Specificity): Studies show this sign has a specificity of about 97% to 98% ^[3][4]. This means that if a baby does not have biliary atresia, the ultrasound will correctly show no sign 97% of the time. While false positives can happen, a clear triangular cord sign strongly supports the suspicion of biliary atresia ^[3][5]. Radiologists often measure the thickness of this tissue (sometimes using a threshold around 3 to 4 millimeters), but this is just a guide, not a strict pass/fail rule ^[6][5]. The doctor will look at the measurement alongside other clinical clues and the radiologist’s overall impression.
• When the sign is absent (Moderate Sensitivity): An ultrasound that does not show the triangular cord sign does not mean your baby is in the clear. Research indicates the sign’s sensitivity is only about 74% to 85% ^[3][5]. This means a significant number of babies who actually have biliary atresia will have a “normal” looking portal vein area on their ultrasound.

The sign can be especially difficult to see early in life. One study found the triangular cord sign in only 17% of affected infants under 30 days old, compared to 56% of those older than 30 days ^[7]. However, visibility also depends on the baby’s unique anatomy, the ultrasound equipment used, and the disease pattern ^[8][5]. You should never wait for your baby to “get older” to see if the sign appears—time is critical in evaluating biliary atresia.

How the Ultrasound Fits into the Diagnosis

An ultrasound is a painless, non-invasive first step in evaluating a baby’s liver ^[9]. During the scan, the radiologist will also check the baby’s gallbladder. While combining gallbladder clues with the triangular cord sign increases the overall accuracy of the test, it is important to know that a normal-appearing gallbladder does not rule out biliary atresia ^[4][5].

Because an ultrasound cannot provide a final diagnosis, a positive triangular cord sign will typically lead to an expedited referral to a pediatric hepatologist (a children’s liver specialist) or a pediatric surgeon ^[10].

Urgent Symptoms to Watch For

A negative ultrasound should never delay further testing if your baby has any of the following time-sensitive symptoms:

• Elevated conjugated bilirubin: This is the “direct” form of bilirubin measured in blood tests, indicating bile is backing up in the liver instead of flowing out ^[11].
• Pale, gray, white, or clay-colored stools
• Dark urine
• Persistent jaundice (yellowing of the skin or eyes)

What Happens Next?

If the care team strongly suspects biliary atresia based on bloodwork, symptoms, and imaging, the most definitive diagnostic test (the “gold standard”) is an intraoperative cholangiogram ^[10]. This is an invasive, major procedure performed under anesthesia in an operating room ^[10]. The surgeon injects a special dye directly into the biliary system to see if the ducts are open or blocked.

It is crucial to understand that if the surgeon confirms biliary atresia during this cholangiogram, they will often proceed immediately with a major operation called the Kasai portoenterostomy while the baby is still under anesthesia ^[10]. This is why it is so important to discuss the full surgical plan, including potential outcomes and recovery, with your care team beforehand.